Drainage system for retractable roof

ABSTRACT

A roof structure to protect a crop growing area includes a retractable roof membrane or curtain that defines pitched sections of the roof. The membrane extends across the valley between pitched sections and apertures are provided in the membrane to allow water to pass through the membrane. A gutter is disposed in the valley beneath the apertures to collect water and discharge it away from the crop growing area.

This application is a continuation-in-part of application Ser. No.08/085,312 filed Jun. 29, 1993, now U.S. Pat. No. 5,513,470, which inturn is a continuation-in-part of application Ser. No. 07/905,781 filedJun. 29, 1992 now abandoned.

The present invention relates to a roof and in particular to a roofsuitable for protecting crops from adverse climatic conditions.

It is well known to provide protection for crops against adverseclimatic conditions by utilizing either a greenhouse structure or byusing a curtain arrangement. The greenhouse structure is well known andutilizes a fixed frame that is glazed to allow light to pass through tothe growing area and to protect the plants within the greenhouse fromthe cold. A more recent development has been a curtain structure inwhich large curtains of material may be deployed across the crop toprovide shade during the day and to prevent heat loss during the night.The curtain structures are more economical than greenhouses in that theyessentially utilize the ambient environment for growing and merelyprotect against extremes. On the other hand, the greenhouse structurewill provide an artificial climate for plants and will frequentlyrequire heating and cooling equipment to maintain a desired environmentwithin the greenhouse.

A conventional glazed greenhouse structure is capable of isolating thecrop from the ambient conditions and so protects the crop from excessivecold or rainfall which may be disastrous to newly sown crops. However,greenhouses are expensive to install, particularly where the protectionthey provide is only required occasionally and suffer from excessiveheat gain during sunny weather. Curtain structures, on the other hand,are more economical to build and maintain and may provide a variety ofprotection to the crops by using different curtain materials. However,when the curtain structure is to be utilized as a greenhouse, thecurtain is effective to control air flow into and out of the structure.Excessive exchange of air leads to high energy consumption for eitherheating or cooling and renders the operation of the greenhouse moreexpensive. The curtain therefore has to be able to cover all of thegrowing area in a relatively airtight manner.

Some difficulty has been experienced with the curtain structurespreviously utilized during heavy rain. To avoid the build-up of water onthe curtain, the curtain has been segmented so that the water simplypasses through the adjacent edges of the curtain onto the crop.Alternatively, a water-permeable material has been used that allows therainfall to fall directly onto the crop. In heavy rainfall, however, theamount of water shed by the roof is significant and can cause washout ofthe newly-sown crop where the water is shed. Moreover, gaps betweenadjacent curtains do not permit effective sealing of the air within thestructure. Similarly, water permeating through the fabric can lead toexcess rainfall on the growing area and materials that are capable ofpassing flow rates associated with heavy rainfall are not generallyeffective to provide the necessary control of the environment within thestructure. For this reason, conventional greenhouse structures have beenretained in areas where heavy rainfall may be expected and newly sowncrops are to be protected.

It is an object of the present invention to provide a roof structurewhich permits the use of a curtain system and obviates or mitigates theabove disadvantages.

According to the present invention, there is provided a roof comprisinga pair of spaced parallel rafter assemblies each having a pair ofoppositely directed rafters diverging upwardly from a valley to arespective peak, a flexible roof membrane extending between said rafterassemblies and from one peak through said valley to an adjacent peak,said membrane including an aperture located in the portion of themembrane extending through said valley, and a water collector disposedbeneath said aperture to collect water shed from said membrane.

By providing apertures in the portion of the membrane extending throughthe valley and collecting water that passes through that aperture, thedischarge of water may be controlled and washout of the crop avoided.

It is preferred that the membrane is retractable allowing full advantageto be taken of favourable climatic conditions, in which case thecontinuity of the membrane facilitates deployment and retraction of thecurtain.

It is also preferred that the apertures are formed as slits in themembrane extending parallel to the valley so that the apertures remainclosed until the weight of water forces the edges of the aperturesapart.

An embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawings, in which

FIG. 1 an end elevation of a roof structure;

FIG. 2 is a plan view of a portion of the roof structure shown in FIG. 1with FIG. 2a showing an alternative embodiment of a portion of the roofstructure shown in FIG. 2;

FIG. 3 is a section on the line 3--3 of FIG. 2;

FIG. 4 is an end view of the portion of the roof structure shown in FIG.3;

FIG. 5 is a perspective view of a portion of the roof structure shown inFIGS. 1-4;

FIG. 6 is a view on an enlarged scale on the line 6--6 of FIG. 3;

FIG. 7 is a view on the line 7--7 of FIG. 2;

FIG. 8 is a view similar to FIG. 7 of an alternative embodiment;

FIG. 9 is a view similar to FIG. 4 of a yet further alternativeembodiment;

FIG. 10 is a general view, similar to FIG. 1, of a still furtherembodiment of a roof structure;

FIG. 11 is an end view similar to FIG. 4 of a further embodiment of postand rafter assembly;

FIG. 12 is an exploded view of the components shown in FIG. 11;

FIG. 13 is a view similar to FIG. 11 of an alternative embodiment of thepost of FIG. 11;

FIG. 14 is a view similar to FIG. 8 showing in section an alternativeembodiment of rafter; and

FIG. 15 is an end view of a still further embodiment of supportstructure for a curtain system.

Referring therefore to FIG. 1, a roof 10 is supported on vertical posts12 to cover a crop growing area 14. The roof 10 includes spaced parallelrafter assemblies 16 that extend from one side of the crop growing area14 to the other and are supported on the post 12.

The roof 10 is formed as a series of gables 15 with valleys 18alternating with peaks 20. The number of gables will vary depending uponthe width of the area 14 and may terminate either at a valley or peakdepending upon the installation. It is, however, more usual to terminateat a valley 18.

The rafter assemblies 16 define the gables 15 and thus the valleys 18and peaks 20. Each rafter assembly 16 includes pairs of oppositelydirected rafters 22 extending from adjacent the valleys 18 to the peak20 to define gable 15. The rafters 22 are connected to the posts 12 inthe valleys 18 to define the rafter assembly 16. Each of the rafters 22is formed from a structural square section tubing, typically ofgalvanized steel tubing, and is connected in the valley 18 to a bracket26 by pins 24. The bracket 26 extends upwardly from a horizontal supportmember 28 which in turn is supported by a pair of inclined members 30that extend from the opposite ends of the support member 28 to the topof the post 12. A triangular aperture is thus formed between the supportmember and the inclined members 30 at the top of the post with therafters 22 being supported above the post 12. The distal end of therafters 22 at the peak 20 are similarly connected through pins andbrackets to the adjacent rafter. The rafter assembly shown utilizes apair of rafters but in some applications a truss may be used for therafter or additional posts 12 may be provided at the peak 20 forstructural support. The exact form of rafter assembly will be determinedby the design loads.

Each of the rafters 22 supports a series of guidewires 32 that extendperpendicular to the rafter assembly 16 and generally parallel to oneanother. The guidewires 32 are secured to each of the rafters 22 atspaced locations and are pretensioned so as to be able to support apredetermined load. As can best be seen in FIG. 2, the guidewires 32 areuniformly spaced along the rafters 22 between the peaks 20 with one ofthe guidewires 32 being located at the peak 20 at the connection betweenadjacent rafters 22. It will also be noted from FIGS. 5 and 6 that aguidewire 32 is provided at the valley 18 as well as to either side ofthe valley 18. The guidewires 32 may be attached to the rafters 22 byany convenient manner such that relative movement between adjacentrafters is opposed by the guidewires. For example, a plate may be weldedto the rafter 22 and a complementary plate bolted to it so that theguidewire 32 may be trapped between the plates after it is pretensioned.Alternatively, where the design of rafter 22 permits, a U bolt may beinserted into the rafter so that the guidewire is trapped between thebight of the bolt and the rafter. As a further alternative, the rafter22 may be drilled so that guidewires 32 pass through the rafters 22 anda cable clamp applied to the guidewire 32 on either side of the rafter22 to inhibit relative movement between the rafter 22 and guidewire 32.In each case, the guidewire provides supports for the rafter assemblyand so acts in a manner similar to the purlins used in a conventionalglazed greenhouse structure.

The guidewires 32 support sections of a flexible roof membrane indicatedgenerally at 34 which is typically formed from a fabric having therequired characteristics to control the environment in the crop growingarea 14. A suitable fabric is Fabrene TGNN available from Fabrene Inc.,North Bay, Ontario, Canada, which is impermeable to water but allows thetransmission of light to the growing area 14. As shown in detail in FIG.6, the membrane 34 is attached to the guidewires 32 by hooks 36 whichare secured in tapes 37 sewn to the membrane 34 and are free to slidealong the wire 32. The nature of the hooks and their attachment to thewire and to the membrane is well known and need not be described furtherat this time. It should, however, be noted that a tape 37 extends alongthe valley 18 to receive hooks 36 and provide support at the valley. Itis, however, possible that the tape 37 and guide wire 32 in the valley18 could be omitted in certain conditions. For example, certain fabricswill not pleat properly in the valley due to the extra stiffnessprovided by the tape.

The membrane 34 includes a leading edge 38 and a trailing edge 40 which,with the membrane deployed, abut adjacent rafter assemblies 16 to coverthe area between the rafter assemblies. The trailing edge 40 is securedto its rafter assembly 16 and the leading edge 38 is formed to provide aseal when it is abutting its respective rafter assembly. As can be seenfrom FIG. 5, the leading edge 38 also includes a rigid tube 42 thatconforms to the shape of the rafters 22 and so defines the profile ofthe leading edge 38 of the roof membrane 34. This ensures that a snugfit is obtained between the rafters 22 and the leading edge 38.

As seen in FIG. 7, the trailing edge 40 of the membrane 34 passesbeneath the rafter 22 and is secured to a support wire 41. The wire 41is set off from the rafter 22 by brackets 43. When deployed, the leadingedge 38 of the adjacent membrane 34 overlaps the trailing edge 40 andhas a flap 45 extending down toward the brackets 43. In this way, acontinuous seal is provided along the rafters 22 when the membrane isdeployed and water running off the leading edge 38 will be collected inthe trough formed beneath the rafter 22 by the trailing edge 40.

As noted above, the membrane 34 is free to slide along with theguidewires 32 between a retracted position in which the leading edge 38is brought close to the trailing edge 40 and a deployed position inwhich the leading edge extends to the adjacent rafter assembly 16 andthe membrane 34 covers the crop growing area 14. In the retractedposition, the roof membrane 34 assumes a folded or pleated configurationwhich will progressively unfold one pleat at a time as the membrane 34is moved to the deployed position. In the deployed position, themembrane will be generally fully extended. Although the membrane 34 willgenerally be taut to inhibit flapping of the material, troughs runningparallel to the rafters 22 will be formed between the locations at whichthe membrane 34 is secured to the cables 32. It will also be understoodthat the areas between adjacent pairs of rafter assemblies 16 each havetheir respective sections of membrane 34 so that one section of membraneextends across the width of the roof 10 between adjacent rafterassemblies 16 but the whole area is covered by several sections of theroof membrane 34.

The membranes 34 may be moved between retracted and deployed positionsby various means, including manually sliding along the guidewires 32,but it is preferred to provide for a mechanized movement. In thisregard, a motorized drum 46 adjacent that drives an endless loop cable50 having upper and lower runs that extend from the drum 46 around apulley 48 and back to the drum 46. The lower run of the loop 50 issecured as indicated at 52 to the leading edge 38 of each of themembranes 34 so that the leading edge 38 moves with the lower run of thecable 50. Thus, upon rotation of the drum 46 in one, direction or theother, the cable 50 can be used to move the membranes 34 betweenretracted and deployed positions with each of the membranes 34 beingmoved in unison. Again, the details of such drives are known and neednot be described further at this time.

It will be noted that the membrane 34 extends continuously from peak 20through the valley 18 to the next peak 20. Ideally, to maximize heatretention and provide uniform growing conditions, a single membrane willextend from one side of the growing area 14 to the other side as acontinuous membrane although for practical purposes it may be necessaryto cover the area between adjacent rafter assemblies 16 in severalsections. To avoid the accumulation of water in the valleys 18, themembrane 34 is formed with apertures 54 in the portion of the membrane34 that passes through the valley 18. An aperture 54 is provided betweeneach of the locations at which the hooks 36 secure the membrane 34 tothe wires 32 so as to be centrally located with respect to the troughsformed in the deployed position.

Apertures 54 are formed in the preferred embodiment as a single slit inthe membrane extending parallel to and along the valley 18. To inhibittearing of the membrane, the slit forming the aperture 54 is located inthe body of the tape 37. Tape 37 is typically woven and has greater tearstrength in both lateral and longitudinal directions than the materialforming the membrane 34. The tape 37 thus provides a local reinforcementfor the membrane 34 around the apertures 54.

The formation of the apertures 54 as a slit also inhibits the air flowthrough the aperture 54. The edges defining the slit will tend to abutone another when the membrane 34 is deployed and so form an effectiveseal. However, when water accumulates in the valley 18, the edges of theslit will be forced apart to allow water to pass through the aperture54. Typically the slits are in the order of 4 inches long with a spanbetween hooks 36 of 16 inches. This has been found adequate toaccomodate heavy rainfall but extreme climatic conditions may dictatelarger apertures.

In certain conditions, it may be preferable as shown in FIG. 2a toprovide the aperture as a pair of intersecting slits so that a largeraperture is provided. This can then accomodate occasional debris such asleaves that otherwise might block the aperture.

The apertures 54 are aligned with the lowest point of the valley 18 soas to be centred above the posts 12. To collect water passing throughthe apertures 54, a gutter 56 is supported on the post 12 between theinclined members 30. The gutter 56 extends from one end of the roof tothe other beneath each of the rafter assemblies 16 and collects waterpassing through the apertures 54. The gutter extends to the end of thebuilding where the water is discharged through a down pipe 58. Tofacilitate drainage, the posts 12 are adjusted vertically so a constantfall is provided from one end of the roof to the other allowing thewater in the gutter 56 to drain effectively to the down pipe 56. Thegutter 56 is formed from a rigid extrusion such as aluminum steel orplastics material. Of course, the gutter 56 may be interrupted along thelength of the building to provide down spouts 58 at regular intervalswhich can then discharge into ground water collection channels ifnecessary.

The membrane 34 thus provides a climate protection fox the groundcovering area 14 which is impermeable to water and therefore protectsthe crop growing area 14 from heavy rain and potential washout. Duringrain the water will flow in the troughs that will be formed between thefastening of the membrane 34 to the guidewires 32 and will flow throughthe aperture 54 into the gutter 56. However, the membrane 34 may beretracted under favourable climatic conditions to avoid the excessiveheat gain normally associated with closed structures, or may be deployedduring parts of the day to provide the shade required for crops in thegrowing area 14. The provision of the apertures 54 and the gutter 56supported on the post 12 provides an effective drainage system for watershed by the roof and thereby permits an impermeable membrane to be usedand avoids damage to the crops or excessive loads being imposed on theroof.

If preferred, a plurality of membranes 34 can be secured between theadjacent rafters 16 and successively deployed in a manner taught in ourco-pending application Ser. No. 07/818,073 filed Jan. 8, 1992 so that anappropriate climate control can be provided to the crop growing area 14as desired. If inclement weather is forecast, it is simply necessary todeploy the impermeable membrane 34 to prevent excess rain being providedto the crop growing area 14. The provision of the apertures 54 andgutters 56 may also be beneficial if permeable material is used, as thepitched roof will tend to shed water in heavy rainfall. Thus the gutterwill prevent damage to the crop and roof structure.

The overlapping of the leading and trailing edges 38,40 described aboveis feasible where a single rafter 22 is used. However, where a truss isused as the rafter assembly 16, it is not practical to pass the membrane34 beneath the rafter. In this case, the arrangement shown in FIG. 8 maybe used. In the embodiment of FIG. 8, like components will be identifiedwith a like reference numeral with a suffix "a" added for clarity.

Rafter 22a is formed as a "top hat" section with laterally extendingflanges 60,62. The edges of the flanges 60,62 are upturned, as indicatedat 64, so that a rigid gutter section is formed on each side of therafter. The flap 45a on the leading edge 38a of the membrane 34a is thusreceived in the gutter and the trailing edge 40a of the adjacentmembrane 34a is held by a wire 66 in the gutter formed by flange 62.Thus rain will be directed by the leading and trailing edgesrespectively into the gutters on the rafters 22a. The gutters terminateat the valley 18a and discharge water into the gutter 56a.

As shown in FIG. 9, it is also possible to offset the gutter 58b andutilize a single post 12b without inclined support members 30. Thus inthe embodiment of FIG. 9, the gutter 58b is formed with a tail 68extending across the valley 18b and under the apertures 54b so as todirect water into the gutter 56b. The tail 68b is notched around theposts 12b allowing a continuous run for the gutter 56b.

In each of the above embodiments, the apertures 54 are shown as alocalized discontinuity in the membrane 34. However, it will beappreciated that the aperture may be formed in different ways, forexample by stapling adjacent edges of membranes so that they move inunison but have apertures or discontinuities between the staples. Inthis way, control over the movement of air and discharge of water isretained.

Alternatively, the membrane 34 may be formed with a highly porous stripin the valley 18 that will pass water while retaining a continuousmembrane. Some loss of control of the air flow may be anticipated withthis arrangement.

The general principles of rainfall control within a greenhouseenvironment may also be used in alternative configurations ofgreenhouse. FIG. 10 shows a sawtooth roof and like components will beidentified with like reference numerals with a suffix "c" added forclarity. In the embodiment of FIG. 10, posts 12c support inclinedrafters 22c. The rafters 22c extend from a peak 20c to a valley 18c withthe post 12c extending vertically to the next peak 20c.

A roof membrane 34c is supported on each of the rafters 22c by wires 32cand may be extended or retracted as described above. The portion of thepost 12c above the valley 18c is also covered with a curtain or may beglazed or louvred if appropriate.

A gutter 56c is supported on the post 12c below the lower edge of themembrane 34c so that water shed from the roof will be discharged intogutter 56c. The gutter 56c is supported on a horizontal cross member 70at each post 12c and drains to one end as described above.

The roof structure shown in FIG. 10 thus simulates a conventionalsawtooth greenhouse structure but retains the flexibility of a curtainsystem while controlling discharge of water from the membrane 34c bylocating a gutter below the membrane in a valley 18c.

A further embodiment of posts and rafter assembly is shown in FIGS. 11and 12 in which like components to those shown in FIGS. 1 to 7 will beidentified with like reference numerals with a suffix "d" added forclarity.

Referring therefore to FIGS. 11 and 12, a post 12d terminates in asaddle 72 which is welded or bolted to the post 12d. The saddle 72 isV-shaped to support a gutter 56d. A post extension 74 has a pair ofout-turned feet 76 which conform to the inclination of the saddle 72.Bolt holes 78 are formed in the feet 76, gutter 56d and saddle 72 toreceive bolts 80 that join the post 12d and the post extension 74.

Rafters 22d are bolted to the upper end of the post extension 74 asdescribed above with respect to FIG. 4.

The post extension 74 is formed from square section steel tubing ofsimilar size to the post 12d. The front and rear walls of the lowerportion of the tubing are removed to provide an aperture 82 and flanks84. The flanks 84 are bent out, as noted above, to provide the feet 76.

With the arrangement shown in FIGS. 11 and 12, the continuous gutter 56dis supported on the saddle 72 with the aperture 82 in the post extension74 allowing water to flow along the gutter 56d. At the same time, arigid support for the rafters 22d is provided by the post extension in asimple yet effective manner and without undue complication.

With the arrangement of FIGS. 11 and 12, the gutter 56d is centrallydisposed to collect water shed by the roof membrane and the channels60,62 if the rafter assembly of FIG. 8 is utilized. The assembly of thestructure remains simple with a minimum of components and adequatelysupports the gutter 56d at the requisite intervals.

The advantages of the post arrangement shown in FIGS. 11 and 12 are alsofound in an alternative embodiment of post illustrated in FIG. 13. Inthis arrangement, however, additional strengths and stability as well asimproved access to the bolts is provided by flaring the flanks 84 sothat they diverge as they extend towards the gutter 56d and the feet 76are bent inwardly. The flanks extend substantially normal to the saddle72 with a gap being left between the feet 76 to allow free drainage ofwater along the gutter 56d.

A further improvement in the sealing of the curtain 40 at the rafters isshown in FIG. 14 which is a view similar to that of FIG. 8. Likecomponents will again be denoted with like reference numerals but with asuffix "e" added for clarity. Referring therefore to FIG. 14, a rafter22e is formed as an inverted channel and a flange 60 extends obliquelyupwardly from the lower end of the channel 22e. The edge 64e of theflange 60e is turned downwardly and arranged to abut the leading edge45e of the curtain 34e as it is moved into a fully deployed position.

Flange 62e is rolled over into a hook shape that receives the round wire66e. The trailing edge 40e of the curtain is wrapped around the wireprior to insertion in the trough 62e so that it is securely held withinthe trough.

Support wire 32e passes above the channel section 22e adjacent to anupstanding plate 90 that is welded to the rafter 22e. A bolt 92 passesthrough the plate 90 into a clamping plate 94 on the opposite side ofthe wire 32e. Tightening of the bolt 92 traps the wire between the twoplates and thus secures it to the rafter 22.

The plate 90 is formed with a projecting hook section 96 that receives aclip 36e. The clip 36e is secured to the curtain 34e and prevents thetrailing edge 40e from being moved along the support wire 32e as thecurtain is deployed. This arrangement avoids excessive strain on thetrailing edge 40a, ensuring that the rod 66 remains firmly locatedwithin the trough 62e.

The arrangement shown in FIG. 14 provides an effective seal between theleading and trailing edges thereby improving the required climatecontrol.

In the arrangements shown in the preceding embodiments, the curtainsupport structure is formed from rafters supporting wires 32 in tension.Under certain conditions, a more robust framework is desirable and inthose circumstances the embodiment shown in FIG. 15 may be utilized. Asuffix "f" has been used for clarity of certain reference numerals. Inthe embodiment shown in FIG. 15, rafter assemblies 16 of are formed astrusses and tubular purlins indicated at 98 extend between the upperchords of the rafters. The purlins are supported above the upper chords22f spacer blocks 100 so that the purlins extend above the flexiblecurtain system indicated at 34f.

The purlins 98 are formed from rigid tubing of either square section asshown or round if preferred, and improve the lateral stability of theroof structure to improve its resistance to wind loads, snow loads andto comply with local building codes. The purlins provide suitablesuspension points for hanging baskets and the like when used forhorticulture and may also be used to suspend lights or wateringequipment where the curtain is to remain retracted for an extendedperiod.

Each of the trusses includes a lower chord 102 that is secured to theposts 12f by yokes 104 bolted to the posts 12f. Yokes 104 include aplate 106 that extends upwardly on the side of the post 12f and iscranked outwardly at its upper end to form one part of saddle 72f. Theupper chord 22f is secured to the saddle 72f by a post extension 74fformed with flanks 84f as described with respect to FIG. 13.

The upper chord 22f and lower chord 102 are connected by struts 108 in aconventional manner.

I claim:
 1. A retractable roof comprising a pair of spaced parallelrafter assemblies each having a pair of oppositely directed raftersdiverging downwardly from a peak to a respective one of a pair oflaterally spaced supports, a plurality of guide means extending betweensaid rafter assemblies at spaced locations and including spaced parallelwires extending generally normal to and supported by said rafters, aflexible roof membrane extending between said rafter assemblies, saidmembrane being suspended from said wires by hooks slidable along saidwires between a deployed position in which said membrane extends betweensaid rafter assemblies to cover the area therebetween and a retractedposition in which the area between said rafter assemblies issubstantially uncovered, one end of said membrane being secured to oneof said rafter assemblies and an opposite end being movable toward andaway from the other of said rafter assemblies, said one rafter assemblyincluding a channel formed on both sides of each of said rafters of saidrafter assembly one of which receives said one end of said membrane andthe other of which projects outwardly to be beyond the other end of anadjacent membrane when in a deployed position thereby to receive watershed from said adjacent membrane.
 2. A roof according to claim 1 whereinsaid membrane extends from one peak through a valley to an adjacent peakand is suspended from said wires at spaced locations and an aperture isprovided in the portion of said membrane extending through said valleyand between each of said locations.
 3. A roof according to claim 2wherein a gutter extends along said valley beneath said membrane.
 4. Aroof according to claim 1 wherein said laterally spaced supports forsaid assemblies are posts located beneath said rafters.
 5. A roofaccording to claim 4 wherein a gutter extends between said posts beneathsaid membrane.
 6. A roof according to claim 4 wherein a gutter issupported by said posts.
 7. A roof according to claim 6 wherein an upperend of said post is bifurcated to receive said gutter and said raftersare supported by said bifurcations.
 8. A roof according to claim 7wherein a support member extends between said bifurcations and saidrafters are connected to said support member between the bifurcationsand above said gutter.
 9. A roof according to claim 1 wherein saidopposite end includes a seal to engage said other of said rafterassemblies.
 10. A roof according to claim 9 wherein said seal includes arigid member conforming to the shape of said rafters between said peaksand secured to said membrane.
 11. A roof according to claim 1 whereineach of said channels is upwardly directed and is operable to directwater into a gutter extending between said rafter assemblies.
 12. A roofaccording to claim 11 wherein said membrane is secured to said rafter bya fastener adjacent to said one end to inhibit movement of said one endaway from said rafter.
 13. A roof according to claim 2 wherein saidaperture is formed by a slid in said membrane.
 14. A roof according toclaim 13 wherein said aperture is formed by a pair of intersectingslits.
 15. A roof according to claim 13 wherein a tape is secured tosaid membrane at the portion thereof extending through said valley toprovide reinforcement for said slit.
 16. A roof according to claim 2wherein said aperture is formed by a porous tape extending along saidvalley.
 17. A roof according to claim 6 wherein said post includes asaddle at its upper end to receive and support said gutter and anextension member extending upwardly from said saddle to support saidrafters, said gutter being located between said saddle and saidextension member and extending laterally of said extension member withsaid extension member being located within said gutter.
 18. A roofaccording to claim 4 wherein purlins extend between said rafterassemblies generally parallel to said guide means and above saidmembrane.
 19. A roof according to claim 18 wherein said purlins aresecured to said rafters by spacers to elevate them above said guidemeans.
 20. A roof according to claim 19 wherein a purlin extends betweenpeaks of adjacent rafters.
 21. A roof according to claim 1 wherein saidone end of said membrane is received in said one channel to secure it toone of said rafter assemblies.
 22. A roof according to claim 21 whereinsaid one end of said membrane is retained in said one channel by aretaining member insertable into said channel.
 23. A roof according toclaim 22 wherein said retaining member is a wire extending along saidchannel.
 24. A retractable roof according to claim 21 wherein said onechannel has a downwardly turned edge to present a smoothly curvedsurface to said one end of said membrane.
 25. A roof according to claim1 wherein each of said channels is upwardly directed.
 26. A roofaccording to claim 25 wherein said other channel is formed by a flangethat extends obliquely upwardly from a lower edge of a rafter of saidrafter assembly.
 27. A roof according to claim 26 wherein an outer edgeof said flange is downwardly turned.
 28. A roof according to claim 25wherein each of said channels is operable to direct water into a gutterextending between adjacent rafter assemblies.
 29. A retractable roofcomprising a pair of spaced parallel rafter assemblies each having apair of oppositely directed rafters diverging downwardly from a peak toa respective one of a pair of laterally spaced supports, a plurality ofguide means extending between said rafter assemblies at spaced locationsand including spaced parallel wires extending generally normal to andsupported by said rafters, a flexible roof membrane extending betweensaid rafter assemblies, said membrane being suspended from said wires byhooks slidable along said wires between a deployed position in whichsaid membrane extends between said rafter assemblies to cover the areatherebetween and a retracted position in which the area between saidrafter assemblies is substantially uncovered, one end of said membranebeing secured to one of said rafter assemblies and an opposite end beingmovable toward and away from the other of said rafter assemblies, saidone rafter assembly including a formation extending along one side ofeach of said rafters of said rafter assembly to receive said one end ofsaid membrane, wherein a hook projects to said one side of said rafteradjacent to at least one of said guidewires and said fastener extendsbetween said hook and said membrane.
 30. A roof according to claim 29wherein said hook is formed on a clamping member secured to said rafterand operable to clamp an adjacent guide wire to said rafter.
 31. A roofaccording to claim 30 wherein said clamping member includes a pair ofplates, one of which is secured to said rafter and has said hook formedthereon and the other of which is movable relative thereto to engage aguide wire passing between said plates.
 32. A retractable roofcomprising a pair of spaced parallel rafter assemblies each having apair of oppositely directed rafters diverging downwardly from a peak toa respective one of a pair of laterally spaced supports, a plurality ofguide means extending between said rafter assemblies at spaced locationsand including spaced parallel wires extending generally normal to andsupported by said rafters, a flexible roof membrane extending betweensaid rafter assemblies, said membrane being suspended from said wires byhooks slidable along said wires between a deployed position in whichsaid membrane extends between said rafter assemblies to cover the areatherebetween and a retracted position in which the area between saidrafter assemblies is substantially uncovered, one end of said membranebeing secured to one of said rafter assemblies and an opposite end beingmovable toward and away from the other of said rafter assemblies, saidone rafter assembly including a formation extending along one side ofeach of said rafters of said rafter assembly to receive said one end ofsaid membrane wherein said one end of said membrane passes beneath saidone rafter assembly and is secured to the opposite side thereof.
 33. Aroof according to claim 32 wherein said one end of said membrane issecured to said formation extending along one side of each of saidrafters of said rafter assembly to receive said one end of saidmembrane.
 34. A roof according to claim 33 wherein said formationextends toward an adjacent rafter assembly so as to be overlapped by theother end of a roof membrane associated with said adjacent rafterassembly when in said deployed position.
 35. A retractable roofcomprising a pair of spaced parallel rafter assemblies each having apair of oppositely directed rafters diverging downwardly from a peak toa respective one of a pair of laterally spaced supports, a plurality ofguide means extending between said rafter assemblies at spaced locationsand including spaced parallel wires extending generally normal to andsupported by said rafters, a flexible roof membrane extending betweensaid rafter assemblies, said membrane being suspended from said wires byhooks slidable along said wires between a deployed position in whichsaid membrane extends between said rafter assemblies to cover the areatherebetween and a retracted position in which the area between saidrafter assemblies is substantially uncovered, one end of said membranebeing secured to one of said rafter assemblies and an opposite end beingmovable toward and away from the other of said rafter assemblies, saidone rafter assembly including a formation extending along one side ofeach of said rafters of said rafter assembly to receive said one end ofsaid membrane, said laterally spaced supports being posts which includea saddle at its upper end to receive and support a gutter and anextension member extends upwardly from said saddle to support saidrafters, said gutter being located between said saddle and saidextension member and extending laterally of said extension member withsaid extension member being located within said gutter and wherein saidextension member includes a pair of feet and an aperture between saidfeet to permit fluid to flow along said gutter from one side of saidpost to another.
 36. A roof according to claim 35 wherein said feet areoutwardly directed to opposite sides of said extension member.
 37. Aroof according to claim 36 wherein said saddle, gutter and feet are eachconfigured to diverge upwardly from said post.
 38. A roof according toclaim 35 wherein said aperture is defined between a pair of flanks thatextend to said feet, said flanks flaring outwardly relative to saidextension member and said feet being inwardly directed.
 39. Aretractable roof comprising a pair of spaced parallel rafter assemblieseach having a pair of oppositely directed rafters diverging downwardlyfrom a peak to a respective one of a pair of laterally spaced supports,a plurality of guide means extending between said rafter assemblies atspaced locations, a flexible roof membrane extending between said rafterassemblies, said membrane being suspended from said guide means andmovable therealong between a deployed position in which said membraneextends between said rafter assemblies to cover the area therebetweenand a retracted position in which the area between said rafterassemblies is substantially uncovered, and a plurality of purlinsextending between said rafter assemblies generally parallel to saidguide means and elevated above said membrane, said purlins being securedto said rafters by spacers to elevate them above said guide means.
 40. Aretractable roof according to claim 39 wherein said guide means includesspaced parallel wires extending generally normal to and supported bysaid rafters, said membrane being secured to said wires by hooksslidable along said wires.
 41. A retractable roof according to claim 40wherein said rafter assemblies are trusses and said rafters form upperchords thereof, said guide wires being supported on said rafters andsaid purlins being connected thereto and elevated therefrom.
 42. Aretractable roof according to claim 40 wherein said membrane extendsfrom one peak through a valley to an adjacent peak.
 43. A retractableroof according to claim 42 wherein said membrane includes an aperturelocated in the portion thereof extending through said valley and agutter is disposed beneath and adjacent to said aperture, said gutterextending along said valley to collect water shed from said membrane andpassing through said aperture.
 44. A retractable roof according to claim43 wherein said rafter assemblies and said gutter are supported onposts.
 45. A retractable roof according to claim 44 wherein said rafterassemblies are formed as trusses having upper and lower chords, saidrafters forming upper chords thereof and being connected to said postsat a location spaced from said lower chord.
 46. A retractable roofcomprising a pair of spaced parallel rafter assemblies each having apair of oppositely directed rafters diverging downwardly from a peak toa respective one of a pair of laterally spaced supports, a plurality ofguide wires extending between said rafter assemblies at spaced locationsand supported thereon, a flexible roof membrane extending between saidrafter assemblies, said membrane being suspended from said guide wiresand movable therealong between a deployed position in which saidmembrane extends between said rafter assemblies to cover the areatherebetween and a retracted position in which the area between saidrafter assemblies is substantially uncovered, and a plurality of purlinsextending between said rafter assemblies generally parallel to saidguide wire, said rafter assemblies being formed as trusses with upperand lower chords and with said rafters forming upper chords thereof,said rafter assemblies being supported on posts with said raftersconnected to said posts at a location spaced from said lower chord andsaid purlins being connected to said rafters and elevated therefrom. 47.A retractable roof according to claim 46 wherein said purlins arelocated above said membrane.
 48. A retractable roof comprising a pair ofspaced parallel rafter assemblies each having a pair of oppositelydirected rafters diverging upwardly from a valley to a respective peak,a plurality of guide means extending between said rafter assemblies atspaced locations, a flexible roof membrane extending between said rafterassemblies, said membrane being suspended from said guide means andmoveable therealong between a deployed position in which said membraneextends between said rafter assemblies to cover the area therebetweenand a retracted position in which the area between said rafterassemblies is substantially uncovered, said membrane including anaperture located in the portion thereof extending through said valley, aplurality of purlins extending between said rafter assemblies generallyparallel to said guide means, and a gutter is disposed beneath andadjacent to said aperture, said gutter extending along said valley tocollect water shed from said membrane and passing through said aperture,said rafter assemblies being formed as trusses with upper and lowerchords and with said rafters forming upper chords thereof, said rafterassemblies being supported on posts with said rafters connected to saidposts at a location spaced from said lower chord, said gutter beingsupported by said posts and located between said upper and lower chords.49. A retractable roof comprising a pair of spaced parallel rafterassemblies each having a pair of oppositely directed rafters divergingdownwardly from a peak to a respective one of a pair of laterally spacedsupports, a plurality of guide means extending between said rafterassemblies at spaced locations and including spaced parallel wiresextending generally normal to and supported by said rafters, a flexibleroof membrane extending between said rafter assemblies, said membranebeing suspended from said wires by hooks slidable along said wiresbetween a deployed position in which said membrane extends between saidrafter assemblies to cover the area therebetween and a retractedposition in which the area between said rafter assemblies issubstantially uncovered, one end of said membrane being secured to oneof said rafter assemblies and an opposite end being movable toward andaway from the other of said rafter assemblies, said one rafter assemblyincluding a channel formed on both sides of each of said rafters of saidrafter assembly one of which receives said one end of said membrane andthe other of which receives the other end of an adjacent membrane,wherein said guide wires are secured to said rafters by respectiveclamping members.
 50. A roof according to claim 49 wherein said clampingmember includes a pair of plates, one of which is secured to said rafterand the other of which is movable relative thereto to engage a guidewire passing between said plates.
 51. A retractable roof comprising apair of spaced parallel rafter assemblies each having a pair ofoppositely directed rafters diverging downwardly from a peak to arespective one of a pair of laterally spaced supports, a plurality ofguide means extending between said rafter assemblies at spaced locationsand including spaced parallel wires extending generally normal to andsupported by said rafters, a flexible roof membrane extending betweensaid rafter assemblies, said membrane being suspended from said wires byhooks slidable along said wires between a deployed position in whichsaid membrane extends between said rafter assemblies to cover the areatherebetween and a retracted position in which the area between saidrafter assemblies is substantially uncovered, one end of said membranebeing secured to one of said rafter assemblies and an opposite end beingmovable toward and away from the other of said rafter assemblies, saidmembrane being secured to said one rafter assembly by a fastenerextending between said rafter assembly and an adjacent one of said hookssuspending said membrane to limit sliding movement thereof along anassociated one of said wires.
 52. A retractable roof according to claim51 wherein said guide wires are secured to an upper surface of saidrafters.
 53. A retractable roof according to claim 52 wherein said guidewires are clamped to said rafters by a clamping member.
 54. Aretractable roof according to claim 53 wherein said clamping memberincludes a pair of plats, one of which is secured to said rafter and theother of which is movable relative thereto to engage a guide wirepassing between said plates.
 55. A retractable roof according to claim51 wherein said fastener projects from said rafter in the direction ofsaid guide wire.
 56. A retractable roof according to claim 55 where saidfastener is rigid.